Integrated Pest Management

            Nematodes are thread-like roundworms invisible to the naked eye. Species parasitic on plants attack roots and other plant parts, causing stunting and yield reduction. Nematode-infected plants are not only weakened, but their root systems are more susceptible to secondary infections by fungi or bacteria. For example, nematode-infested okra plantings are often attacked by Fusarium wilt. Not all nematodes are plant pathogens. The majority of nematode species live in the soil on decaying plant material where they are active in decomposition and nutrient recycling. Some species parasitize other nematodes or insects.

            Correct identification is the first step when a nematode problem is suspected. The second step is to determine whether populations are high enough to threaten the crop.  Root knot nematodes, the most common pathogenic nematodes in vegetables.

          Nematode problem can be  minimized  by adopting cultural practices and if not controlled, chemical control methods  can be adopted.

Root knot nematode (Meloidogyne incognita, M. javanica, M.arenaria, M.halpa)

Identification

• Root knot nematodes are microscopic roundworms, obligate endo-parasites.

• The root-knot nematodes are widely distributed in nurseries and uplands or in well-drained soils all over India.

Damage

• Nematodes damage cotton by attacking the young tap and secondary roots. Their feeding stimulates the production of galls. 
• These galls interfere with the roots ability to absorb  water and nutrients, and provide locations for other disease-producing organisms, such as fungi (Fusarium) or bacteria, to readily enter the plant.
• Chlorosis, wilting, delay in flowering and fruit formation, reduction in plant size, yield etc. may be noted in above ground parts of infected plants
• Distinct galls shaped like spindles, beads or clubs, develop around the position where nematode places  itself in the root of the plant.

Cultural Control

• Deep summer ploughing 
• Crop rotations with non-host crop
• Use of resistant varieties 
• Soil solarization using clear thins polythene cover for 3-6 weeks in summer has been also found very effective. 
• Plough the main field twice in summer reduces nematode population and crop damage.
• If injury is high, soil fumigation may be needed.
  

Chemical Control

• The soil treatment of nursery beds with carbofuran @ 0.3 g a.i./ sq.m. 
• Root dip treatment with systematic pesticides and hot water treatment of dormant infected planting material before transplanting in the main field is also recommended

Root-Lesion Nematode (Pratylenchus spp)

Identification

• The above ground symptoms of damage by these nematodes are non-specific. 
• Pratylenchus spp. Include a number of species, which are widely distributed in India. 
• They have wide host range including important crops like wheat, bajra, maize, coffee, oats, barley, 
  cotton, potato, rice, soybean, sugarcane, vegetables, ornamental and fruit crops.

Damage

• Yellowing and stunting of tops may occur. 
• Loss of primary roots, severe pruning of roots, reduced size of blossom, shrinking of grains and
  reduced plant growth are associated with the nematode. 
• The most characteristic symptom, however, is production of lesions on roots, the extent of which 
  may vary with nematode population density and host varieties. 
• The lesions appear as tiny, elongate water soaked  spots which soon trub brown to almost black. 

Cultural Control

• Hot water treatment of bulbs, corns, tubers, and fleshy roots can control the dormant nematodes residing in them. 
• Growing of Tagetes patula cv. Harmony, autumn after main crop or between rows of main crop has been found quite effective management method. 
• Summer ploughing of field reduces population density. 
  

Chemical Control

• Application of carbofuran or phorate @ 1-2 kg a.i./ha at sowing reduces crop damage.

Spiral nematode (Helicotylenchus multicinctus)

• Mild stunting and reduced yields occur where populations are large.
• Small light to dark brown lesions may also occur on infected plants.

Pigeon pea Cyst nematode (Heterodera cajani)

Identification

• Heterodera cajani is a widely prevalent parasite of mainly leguminous crops.
• The second stage juveniles attack the roots and develop to produce lemon shaped white females
  protruding out of root.
• The female deposits many eggs in a large gelatinous eggs but retains some in body, which after death turns into a brown cyst.
• The nematode completes the life cycle in 3-4 weeks and has several generations in a single crop season.

Damage

• The crop shows yellowing and stunted growth with poor pod formation.
• Soybean crop in MP has also been found infected with these nematodes.

Cultural Control

• Summer ploughing of the field and crop rotation for 2-3 years with cereals may reduce nematode population densities.
  

Chemical Control

• Application of carbofuran or phorate @ 1-2 kg a.i./ha may also reduce crop damage

Soybean cyst nematode (Heterodera glycines)

Identification

• It is a small plant-parasitic roundworm that attacks the roots of soybeans.
• In its juvenile form, it penetrates soybean roots. Those that become females lose the ability to move,
  enlarge into a lemon-shaped "white female," which breaks through the root surface, dies, and turns into a brown cyst or egg case.

Damage

• The disease is characterized by patchy growth, stunted, yellowish plants. Infected plants exhibit
  fewer leaves, reduced tillering, delayed emergence of ears, reduced number of spiklets and grains.
• Presence of cysts on the roots or in soil is the only confirmatory indication of nematode infestation.

Cultural Control

• Maintain proper fertility and soil pH levels in SCN-infested land.
• Maintain good sanitation.
• Use resistant varieties.
  

Chickpea Cyst nematode (Heterodera sp.)

Identification

• Heterodera cajani is a widely prevalent parasite of mainly leguminous crops.
• The second stage juveniles attack the roots and develop to produce lemon shaped white females
  protruding out of root.
• The female deposits many eggs in a large gelatinous eggs but retains some in body, which after death turns into a brown cyst.
• The nematode completes the life cycle in 3-4 weeks and has several generations in a single crop season.

Damage

• The crop shows yellowing and stunted growth with poor pod formation.
• Soybean crop in MP has also been found infected with these nematodes.

Cultural Control

• Summer ploughing of the field and crop rotation for 2-3 years with cereals may reduce nematode population densities.
  

Chemical Control

• Application of carbofuran or phorate @ 1-2 kg a.i./ha may also reduce crop damage

Lance nematode (Hoplolaimus sp.)

Identification

• These are ecto-parasites, sometimes semi-endo-parasites.
• Lance nematodes, Hoplolaimus spp., are large nematodes which are highly resistant to effects of
  temperature extremes and dry soil conditions.
• Larvae look similar to adults except that they are smaller.
• This group of nematodes is easily detected with soil sampling.

Damage

• Lance nematodes feed externally along root surfaces but may also feed with at least part of the
  body embedded in the root.
• Roots damaged by lance nematodes may be darkened and restricted in their development.
• Above-ground symptoms include yellowing, stunting, and sometimes death of plants.

Cultural Control

• Crop rotation with peanuts.
• Weed control
  

Chemical Control

• Dimethoate or carbofuran at the rate of 1 kg /ha is effective for controlling hopolaimus.

Reniform nematode (Rotylenchulus reniformis)

Identification

• The term 'reniform' refers to the kidney-shaped body of the mature female.
• They are semi-endoparasitic (partially inside roots) species in which the females penetrate the root
  cortex, establish a permanent-feeding site in the stele region of the root and become sedentary or
  immobile.
• If the infected roots are dipped in 0.25% trypan blue and rinsed in water, the nematode egg sacs are selectively colored blue while roots are not stained.

Damage

• Infected plants generally grow less vigorously than healthy ones.
• Infected plants have smaller root systems than healthy ones.
• Infected roots appear dirty because of nematode egg sacs.

Cultural Control

• Summer fallow and ploughing.
• Clean cultivation.
• Growing antagonistic/trap crops like african marigold, asparagus and crotalaria.
• Grow resistant varieties.
• Select fields with no previous record of nematode infestation.
• Rotate crops with rice maize or groundnut to reduce nematode populations.
• Solarize soil in summer to reduce nematode populations.
  

Chemical Control

• Seed treatment with 1-3% carbofuran by weight, application of non-edible seed cakes of neem, Maha, Castor etc., are useful in management of this nematode.

Stubby Root nematode (Trichodorus christei)

Identification

• Stubby-root nematodes generally do best in sandy soils and are capable of considerable vertical
  migration.
• These are very small and can be seen only with the aid of a microscope.
• They are ectoparasitic nematodes, meaning that they feed on plants while their bodies remain in the
  soil.

Damage

• These nematodes feed mostly at root tips, thereby stopping root growth.
• As new root growth continues to be stopped by feeding of stubby-root nematodes, the root system
  takes on a characteristic "stubby-root" appearance.
• Affected root tips may be "stubbed" without discoloration or a slight discoloration may be evident.
• These injured plants exhibit a small root system with fewer and shorter secondary roots than would have otherwise been present.
• Above-ground symptoms are the typical symptoms of nematode damage: stunting, yellowing, and slow growth. Plants are rarely killed by stubby-root nematodes

Kalahasti malady (Tylenchorhynchus brevilineatus)

Identification

• Ecto-parasite on epidermal cells between root hairs in zone of elongation.

Damage

• Infected plants appear in patches in the field and stunted with greener than normal foliage.
• Small, brownish lesions appear on the pegs, and on young developing pods.
• Small, brownish lesions appear on the pegs, and on young developing pods.
• In advanced stage, entire pod surfaces become blackened.
• Discolouration can also be observed on roots.

Cultural Control

• Grow resistant varieties
• Sow after rice.
• Irrigate the field.
  

Chemical Control

• Apply carbofuran 3G once in 4 years at 4 kg active ingredient (133) kg/ha 25-30 days after sowing along with irrigation water.

Stunt Nematode (Tylenchorhynchus spp.)

Identification

• They are ecto-parasites, medium-sized nematodes.
• Nematode prefers sandy soils.
• All stages are parasitic; average feeding time is 10 min.

Damage

• Primarily feed ecto-parasitically cells of roots in the region of root elongation but sometimes embedded partly or totally in the root tissues.
• The nematode feeding results in stubby root condition leading to stunting and reduced plant
  growth.